Mobile devices have become ubiquitous in today's world and are increasingly used to perform various functions such as streaming multimedia content, playing high definition online games, enabling video calls, and so forth in addition to basic voice calls. Each of these functions and other functions requires network resources. It is therefore important to efficiently and effectively charge (i.e., bill) such communication sessions and provide optimized services.
Typically, there are 2 kinds of charging (billing) to users in communication networks: Offline Charging and Online Charging. In case of offline charging, the call detail records or charging data records (CDRs) are collected at appropriate network elements (NEs) in the network (e.g., at the packet data network (PDN) gateway (PGW) in case of a long term evolution (LTE) network) during a user session, and sent to the charging data function (CDF) at regular intervals and/or at the end of a user session. The CDR may include information such as users involved in the session, resources used for the session (e.g., bandwidth, bytes of information exchanged, codecs), services invoked during the session (e.g., forwarding, conference), session start and stop timestamps, etc. The CDR may also include metering units that were consumed for the session. The network element that sends the CDR to the CDF is also referred to as charging element or as charging trigger function (CTF). The CDF may further send the received CDR(s) directly or via the charging gateway function (CGF) to the billing domain (BD) which may be a part of the business support system (BSS). The BSS then uses these received CDR(s) to determine the amount to be charged to the user for the session. Thus, offline charging involves post processing after the session ends and is typically used in the post-paid charging scenario.
In case of online charging, the online charging system (OCS) triggers the appropriate NEs in the network to compare the entitlement of the user versus the charges of resources used in real-time. The OCS then determines the cumulative charges for the resource usage by the user and decides to terminate the user session in case the charges exceed the user entitlement. In such a case the OCS may trigger termination or may direct the NE to terminate the session. Thus, online charging involves taking actions based on the user entitlement in a real-time manner when the user's session(s) is in progress. Online Charging is usually preferable from a functionality and user experience aspect. However, online charging is also more demanding with respect to network resources and thus, a network may have less capacity to support online charging. In particular, in the context of heterogeneous networks, service and session continuity typically spans across multiple different networks. Under such scenario with user sessions spanning across multiple heterogeneous networks, the online charging specifically gets complicated leading to inaccurate charging (under/over-charging).
In one scenario, a particular user session may simultaneously span across multiple access networks, e.g., LTE and Wi-Fi. In other words a user session is split across multiple access networks. For accurate charging, the charging element should be able to obtain information in real-time about the resource consumption by the session that spans over each of those access networks. However, obtaining information on real-time resource consumption across multiple access networks is not possible. This is because of the lack of interface and interaction between the OCS and the NE that performs the session-split (e.g., if eNodeB performs the session split), or because the NE that performs the session-split is not capturing and reporting the access level resource consumption information in real-time (e.g., if PGW performs the session split). No standard mechanism exists for reporting the resource consumption over each of these access networks, hence compounding the issue in scenarios involving user mobility across networks. Existing techniques provide a mechanism of allocating separate quotas during session establishment, per access network to user sessions spanning different access networks. Existing techniques also provide allocation of additional quota from the network on request. However, the mechanisms provided by existing techniques have limitations of monitoring consumption of user quota on individual networks during the user session. The limitation is that the monitoring consumption of user quota on individual networks can be performed only if the PDN Gateway (PGW) is aware of the session split, and the number of packets routed via each of the access networks. For example, when the session-split happens in the Radio Access Network (RAN), the eNodeB performs the session-split between LTE and Wi-Fi. Thus, the Core NEs are unaware of the session-split, and the eNodeB does not perform charging related functions. The eNodeB or any other Core-NE therefore fails to perform proper monitoring of consumption of user quota. An obvious solution to overcome this limitation may be to introduce charging functionality and appropriate online charging interface at eNodeB. However, during handover (HO), roaming and session-offloading condition, this solution fails to work.
In another scenario, a user may have one or more active sessions with varying priorities, and a particular session gets offloaded at any point of time onto another network, thereby causing change in charging element resulting in disparate charging due to the fact that the new charging element may not have the same capability or granularity of monitoring the resources consumed for the session, etc. Existing techniques provides a mechanism of online charging when offloading to WLAN and via a local network without going via the wireless packet core network. However, these techniques do not address the granularity of monitoring the resources consumed for the session (e.g., only a flat rate charging may be provided). Hence the mechanisms proposed in these existing techniques may lead to inaccurate charging. Also, these existing techniques do not cover handover and roaming/mobility scenarios with respect to the information to be exchanged, interfaces, etc. with the OCS. Hence, the online charging mechanism fails to work in such scenarios. Thus, the existing techniques fail to address online charging effectively in scenarios involving user session handover across heterogeneous networks due to differences in capabilities and granularity of monitoring, and the lack of information exchanged in real-time between the charging entities.
In yet another scenario, the user may be roaming where the session may be routed without involving the home network. Also, lack of interaction among the charging elements of different networks in case of online charging during optimized session routing using the principles outlined in the “Study on roaming architecture for voice over IP Multimedia Subsystem (IMS) with local breakout” (3GPP TR 23.850 Release 11.0.0), “Optimal media routing (OMR) within the IP Multimedia Subsystem (IMS); Stage 3” (3GPP TR 29.079 Release 11.3.0), and/or “Study on Stage 2 aspects of Optimized Service Charging and Allocation of Resources (OSCAR) in the IP Multimedia Subsystem (IMS) whilst roaming” (3GPP TR 23.849 Release 11.0.0) between the visited and/or home network of the calling user and the home and/or visited network of the called user, leads to failure in online charging. Existing techniques provide mechanism of CDR generation by the visited mobile network (V-PLMN) (e.g., Visited Call Session Control Function (V-CSCF)) and sending it to the CDF in case of sessions involving a roaming user. However, it fails to provide interaction between the charging entities in the different networks and OCS(s) in case of a roaming user, leading to failure of online charging.
In fact, all the above discussed scenarios may be possible for a single user simultaneously, that is likely to lead to incorrect charging or failure in online-charging and unexpected termination of user sessions. Further, existing techniques typically recommends termination of the session upon exhaustion of the user quota. As a consequence improved service offering by making the best use of available network resources without violating policies is not possible especially when the cumulative cost of resource consumption approaches the user-quotas or reaches the user-quota limits. This is because appropriate actions on user sessions taking into consideration user priorities, dynamic network conditions, historical data, etc. is not done instead of simply deciding to terminate the user session(s).
The above problems or issues are caused due to following limitation in the existing mechanisms in online charging scenario across heterogeneous networks: (a) inadequate exchange of online resource consumption information in real-time with the appropriate entities (OCS) across heterogeneous networks is a challenge due to protocol, capability mismatch, granularity and frequency of such shared information, (b) insufficient granularity and frequency of monitoring resources consumption by OCS in a user-session (from a charging perspective), and analyzing such information for determination of cumulative resource charges, and (c) user session termination based on pre-assigned quota at the beginning of the session without taking into consideration user-entitlement, user-preferences, network conditions and real-time resource consumption information of all sessions for the user. Existing techniques of online charging thus fail to address the above limitations.